raghu,

there is technique that has been discussed (or mentioned) around the forum, using a clocked signal to scan a keyboard. I can't remember the details, but is something related to sending a clock, the clock shifting a pulse to a key at time, if the key is pressed you can identify it.

It's used in videogame controllers like the ones of super nintendo, playstation and others.

look at a playstation controller, around 20 keys and only 9 pins... only 5 pins control the key presses... probably a clock, a data in, reset data out...

that site has a better and accurate description of the procces:

http://snespad.emulationworld.com/f_snes.html

hth

orlando